A principal open set of an affine scheme 
is a set of the form
 |
where 
.
Principal open sets form a basis for the Zariski
topology, and 
is naturally isomorphic to 
.
Principal Open Set
See also
Affine Scheme, Ring Spectrum, Structure Sheaf, Zariski TopologyExplore with Wolfram|Alpha
References
Hartshorne, R. Algebraic Geometry. New York: Springer-Verlag, 1977.Cite this as:
Weisstein, Eric W. "Principal Open Set." From MathWorld--A Wolfram Resource. https://mathworld.wolfram.com/PrincipalOpenSet.html